Hydraulic fluids

ABSTRACT

AN IMPROVED HYDRAULIC FLUID IS PROVIDED, WHICH COMPRISES A COMBINATION OF TWO ESTERS; ONE BEING A DI (OXYALKENE) OR DI (POLYOXYALKENE) ESTER OF A DIBASIC CARBOXYLIC ACID, E.G. IN AMOUNTS OF 30% TO 60% BY WEIGHT; AND THE OTHER BEING AN ESTER OF A DIOL, PARTICULARLY A GLYCOL, AND A MONOBASIC CARBOXYLIC ACID, E.G. IN AMOUNTS OF 25% TO 55% BY WEIGHT.

States ate 3,825,497 HYDRAULIC FLUIDS Robert Alan Cameron Ker, London,England, assignor to Castrol Limited, London, England No Drawing.Continuation of abandoned application Ser.

No. 33,881, May 1, 1970. This application Apr. 28,

1972, Ser. No. 248,774

Int. Cl. C09k 3/00 US. 'Cl. 252-79 Claims ABSTRACT OF THE DISCLOSURE Animproved hydraulic fluid is provided, which comprises a combination oftwo esters; one being a di (oxyalkene) or di (polyoxyalkene) ester of adibasic carboxylic acid, e.g. in amounts of 30% to 60% by Weight; andthe other being an ester of a diol, particularly a glycol, and amonobasic carboxylic acid, e.g. in amounts of 25% to 55% by weight.

This is a continuation of application Ser. No. 33,881, filed May 1, 1970and now abandoned.

BACKGROUND OF THE INVENTION where R is a straight or branched chainalkylene group which contains at least 2 carbon atoms, R is an alkylradical having from 1 to 4 carbon atoms or a phenyl radical, R isethylene, propylene or butylene and n is an integer of from 0 to 3.British Patent Specification No. 1,083,324 also describes and claims ahydraulic fluid having a kinematic viscosity at -40 C. of not more than5000 cs. and comprising at least 50% by weight of at least one esterhaving the general formula /COOR (OR OR R COORHOR UROR where R isstraight or branched chain alkylene group which contains at least 2carbon atoms, R is an alkyl radical having from 1 to 4 carbon atoms or aphenyl radical, R is ethylene, propylene or butylene and n is an integerof from 0 to 3 together with a minor proportion of a polyoxyalkyleneglycol or polyoxyalkylene glycol ether. Useful brake fluids have beenformulated in accordance with that patent but it has not yet been foundpossible to formulate a fluid which conforms with all the most stringentspecifications of various manufacturers of automobiles and hydraulicsystems.

SUMMARY According to the present invention there is provided animprovement in and/or a modification of the hydraulic system claimed inclaim 1 of Britsh Patent Specification No. 1,083,324 which contains, asthe functional fluid, a

3,825,497 Patented July 23, 1974 wherein R is a straight or branchedchain alkylene radical or mixture of straight or branched chain alkyleneradicals containing from 2 to 4 carbon atoms; R R R and R are the sameor different and each is an ethylene or propylene radical; R and R arethe same or different and each is a methyl or ethyl radical; and p, q, sand t are integers such that the total number of carbon atoms in R R Rand R is from 6 to 10 and such that if either s or t is zero the otheris at least one and if either p or q is zero the other is at least one;and ester B having the general formula:

wherein R and R are the same or different and each is an ethylene orpropylene radical; and l and m are integers such that the total numberof carbon atoms in R and R is from 5 to 9.

PREFERRED EMBODIMENTS OF THE INVENTION Preferably the total number ofcarbon atoms in R R R' and R is from 7 to 9 and more preferably ester Ahas the general formula:

wherein R R and R have the same significance as hereinbefore describedand wherein R and R are preferably methyl and R is preferably derivedfrom a mixture of adipic, glutaric and succinic acids. It isparticularly preferred that this mixture of acids consists of 15% to 40%adipic, 40% to glutaric and 15% to 35% succinic acid, the percentagesbeing by weight.

Preferably the total number of carbon atoms in R and R is from 6 to 8,particularly 6. In a particularly preferred embodiment of the inventionester B is a triethylene glycol dipropionate, dipropylene glycoldipropionate or a mixture of dipropionate esters derived from low cutco-condensates of ethylene and propylene oxides, e.g. diethylene oxapropylene glycols and dipropylene oxa ethylene glycols.

Preferably the acidity of ester B should not exceed 0.1 mgm. KOH/ g.

The fluid may contain from 3% to 10%, by weight based on the weight ofthe fluid, of a polyoxyalkylene glycol or ether thereof, whichpreferably has the general formula:

wherein R is an alkylene radical, or a mixture of alkylene radicals,containing from 2 to 4 carbon atoms, R is a hydrogen atom or an alkylgroup containing 1 to 3 carbon atoms and u is an integer from 2 to 4.Preferably R is an ethylene radical, R is an ethyl group and u is 3.

The fluid may also contain a minor amount, for example from 1% to 10%,preferably 2% to 5%, by Weight, based on the weght of the fluid, of areaction product of ammonia or an amine and an alkylene oxide or mixtureof alkylene oxides, preferably ammonia and propylene oxide.

The fluid also may contain a lubricity additive such as glycol di basicacid polyesters, for example in an amount from 1% to 7%, preferably 3%to 5%, by weight, based on the weght of the fluid, or a complex ester.In one embodiment of the invention the polyester is derived from one ormore dibasic acids such as:

glutaric acid succinic acid phthalic acid ethylene glycol 1,2 propyleneglycol neopentyl glycol 1-4 butane diol 1-6 hexane diol andpolyoxyalkylene glycols such as:

di propylene glycol tri propylene glycol.

di ethylene glycol tri ethylene glycol Preferably the lubricity additivehas an acidity of less than 2.0 mgm. KOH/ g. when determined by IPmethod 1.A. This can be achieved by using an excess of glycol or endstoping with a C -C alkanol during its preparation. The molecular weightof the polyester or complex ester is preferably from 500 to 3,000, morepreferably from 600 to 2,000.

The fluid of the present ivention may also contain known corrosioninhibitors and additives to maintain the pH above 7.0, for examplebis(3,4-epoxy-6-methyl-cyclohexylmethyl adipate.

The fluid preferably contains to 60%, more preferably to by weight ofester A and 25% to more preferably 30% to 50%, most preferably 35% to45%, of ester B, the percentages being by weight based on the weight ofthe fluid.

The present invention also provides the hydraulic fluids which comprisea mixture of the two esters A and B, as hereinbefore described. Thepresent invention further provides a method of operating a hydraulicsystem, which method comprises introducing into the hydraulic system ahydraulic fluid comprising a mixture of the two esters A and B, ashereinbefore described and transmitting power by applying pressure tothe hydraulic fluid.

The invention will now be illustrated with reference to the followingexamples, in which all parts are by weight.

EXAMPLE 1 Parts Ester A Triethylethylene glycol dipropionate 40 Ester Awas an ester of diethylene glycol monomethyl ether and a mixture ofadipic acid (30.2%), glutaric acid (49.2%) and succinic acid (20.6%).

EXAMPLE 2 Parts Ester A 60 Tirethylene glycol dipropionate 30Triethylene glycol monoethyl ether 1O EXAMPLE 3 Parts Ester A Diethyleneglycol dipropionate 20 Triethylene glycol monoethyl ether 10 EXAMPLE 4Parts Ester A2 Ester B 35 Triethylene glycol monoethyl ether 7 Amine A[a condensation product of propylene oxide (5.5 moles) with ammonia (1mole)] 3 Ester A was a similar ester to Ester A except that theproportions of adipic, glutaric and succinic acids were 16.6%, 57.8% and25.6% respectively.

Ester B was a co-condensation product of 2 moles ethylene oxide with onemole of propylene glycol esteri- 4 fied with propionic acid and had aviscosity of 597 cs. at 40 F. and an SAE boiling point of 530 F.

The blends of Examples 1 to 4 were all found to be adequate brakefluids.

EXAMPLE 5 Parts Ester A 55 Tirethylene glycol dipropionate 35 Ethyltriglycol 7 Amine A 3 Dibutylamine 0.1 Benzotriazole 0.1 Triphenylphosphite 0.15

This blend passed all the requirements of the SAE J 1703 specification.

EXAMPLE 6 Parts Ester A 42 Triethylene glycol dipropionate 45Triethylene glycol monoethyl ether 1 7 Amine A 3 Lubricity additive 3Dibutylamine 0.1 Benzotriazole 0.1 Triphenyl phosphite 0.15

The lubricity additive was a complex ester sold under the trade nameReoplex 641, which had a molecular weight of 712 and was derived fromneopentyl glycol and a mixture of sebacic, azelaic and adipic acids, theproportions of the acids in the mixture being determined, by analysis,as 53%, 5% and 38% respectively.

This blend passed the requirements of the SAE 11703 specification andspecifications laid down by the brake manufacturers and automobilemanufacturers.

EXAMPLE 7 Parts Ester A 39 TEGDP (triethylene glycol dipropionate) 45Triethylene glycol monoethyl ether 5 Triethylene glycol monomethyl ether5 Amine A 3 Reoplex 641 3 Dibutylamine 0.05 Benzotriazole 0.05 Ageriteresin D 0.05 Armeen 12D 0.1 Triphenyl phosphite 0.15

Agerite resin D is a commercially available polymerised trimethyldihydro quinoline resin and Armeen 12D is a commercially availablesaturated stright chain pri mary amin wherein the straight chain is C3.5% C14 and C10.

EXAMPLES 8 TO 14 The blends of these examples were the same as Example7, except in that the ester A and triethylene glycol dipropionate werereplaced by other esters as follows:

Example 8 30 parts DEDGS [the ester of diethylene glycol monoethyl etherand succinic acid]; 54 parts triethylene glycol dipropionate Example 930 parts DMDGS [the ester of diethylene glycol mono methyl ether andsuccinic acid]; 54 parts triethylene glycol dipropionate Example 10 55parts DEDGA [the ester of diethylene glycol monoethyl ether and adipicacid]; 29 parts triethylene glycol dipropionate Example 11 54 partsDMDGA [the ester of diethylene glycol monomethyl ether and adipic acid];30 parts triethylene glycol dipropionate Example 12 45 parts DEDGN [theester of diethylene glycol monoethyl ether and a mixture of adipic acid(30.2% glutaric acid (492%) and succinic acid (20.6%)]; 39 partstriethylene glycol dipropionate Example 13 45 parts DEDGG [the ester ofdiethylene glycol monoethyl ether and glutaric acid]; 39 partstriethylene glycol dipropionate Example 14 54 parts DMDGG [the ester ofdiethylene glycol monomethyl ether and glutaric acid]; 30 partstriethylene glycol dipropionate.

The rubber swell characteristics of the blends of Examples 7 to 14 weredetermined by immersing a SBR (styrene-butadiene rubber) cup in theblends for 3 days at 120 C. and measuring the change in diameter of thecup. Further rubber swell characteristics determinations were made bythe Archimedean principle described in British Patent Specification No.1,083,324 by immersing samples of a synthetic rubber (designated G9) anda natural rubber (designated R32) in the blends. The results obtained,and other properties, are compared in the following Table with theresults obtained, and the prop erties of, the esters (unblended) formingthe major constituents of the blends.

wherein R is a straight chain alkylene radical containing from 2 to 4carbon atoms and R and R are the same or different and each is a memberselected from the group consisting of a methyl radical and an ethylradical; and ester B being present in an amount of from 25% to 50% byweight and consisting of triethylene glycol dipropionate.

2. The fluid of claim 1 wherein ester A is a mixture of esters derivedfrom a mixture of from 15% to 40% by weight adipic acid, 40% to 60% byweight glutaric acid and 15% to succinic acid.

3. The fluid of claim 1 which also contains from 3% to 10% by weight,based on the weight of the fluid, of a polyoxyalkylene glycol or etherthereof having the formula:

H(OR ),,OR

wherein R is a member selected from the group consisting of alkyleneradicals containing from 2 to 4 carbon atoms and mixtures thereof, R isa member selected from the group consisting of a hydrogen atom and analkyl group containing from 1 to 3 carbon atoms and u is an integer offrom 2 to 4.

4. The fluid of claim 3 wherein R is an ethylene radical, R is an ethylgroup and u is 3.

5. The fluid of claim 1 which also contains, as a lubricity additive,from 1% to 7% by weight, based on the weight of the fluid of a polyesterhaving a molecular weight of from 500 to 3,000 and derived from adibasic acid selected from the group consisting of sebacic acid, azelaicacid, adipic acid, glutaric acid, succinic acid, phthalic acid andmixtures thereof and a diol selected from the group consisting ofneopentyl glycol, 1-4 butane diol, 1-6 hexane diol, ethylene glycol,1,2-propylene glycol, di ethylene glycol, tri ethylene glycol, dipropylene glycol and tri propylene glycol.

SB R cup Viscosity Chemical 3 days at Shore G9 rubber, percent R32rubber, percent at C. stability, B.P. 120 C hardness,"

( F.) mm degrees 3 days 7 days 3 days 7 days TE GDP 670 +1 560 +1.91 -1330. s 31 6 7. 3 7. 4 12. 9 14. 6 4. 0 3.8 6. 9 8.2 20. 8 20. 8 4. 0 6. 318. 1 3. 5 16. 7 16. 5 4. 0 5. 2 7. 5 1.1 18. 6 20. 2 4. 8 5. 7 14.1 5.5 13. 9 14. 5 2. 8 3.3 31. 2 0. 6 22. 2 20. 9 8.1 4. 9 17. 6 6. 2 19. 721.0 5.0 4. 8 19. 7 17. 2 2. 4 2. 4 11. 0 l1. 6 2. 9 3. 5

According to S.A.E. J 1703 Specification. "Shore Hardness of SBR cupalter immersion as compared with Shore Hardness before immersion. "Nochange.

In general the results obtained in these rubber swell characteristicsdeterminations were at least as good as, and in many cases substantiallybetter than, the characteristics which would have been expected from atheoretical calculation thereof on the basis of the rubber swellcharacteristics of the individual constituents of the blends.

The fluids of the present invention also have the advantage of very lowhygroscopicity and are similar in this characteristic to the fluidsdescribed in British Patent Specification No. 1,083,324.

I claim:

1. A hydraulic fluid consisting essentially of a mixture of two esters Aand B, ester A being present in an amount of from 30% to by weight andconsisting of at least one compound of the formula:

00 o cimo 0,110 R References Cited LEON D. ROSDOL, Primary Examiner H.A. PITLICK, Assistant Examiner US. Cl. X.R. 252396

